Answer to the Letter to the Editor of Miao Yu et al. concerning “Is L5-S1 motion segment different from the rest? A radiographic kinematic assessment of 72 patients with chronic low back pain” by AB Sabnis et al. (Eur. Spine J; 27(5):1127–1135)

[摘要] We would like to thank the authors of the letter for showing interest in our work. Undoubtedly, the disc height and spinal alignment will be altered in the supine position compared with the standing position, and it will be useful to evaluate the relationship between kinematics and degenerative changes in the standing position. An upright magnetic resonance (MR) scanner allows the patient to be scanned in the standing and several other weight-bearing positions [1]. However, currently available upright MR scanners generate relatively low magnetic feld strengths ranging from 0.2 to 0.6 Tesla, and the acquired images are characterised by lower resolution and lower signal-to-noise ratios than the high-feld recumbent MR scanners [2, 3]. Since our study was retrospective in nature, this option was not available to us.